!!WARNING!! High Voltage Connections inside. Beware during the process. I am not responsible for any short circuit of damage to you. Do it on your own risk.
The circuit above has been tested and is working well.
Power Saving has been the biggest issue so far, Sometimes people forget to turn off the lights on staircase at night. Imagine a skyscraper of 100floors. Staircase must be consuming around 500W+ of power itself during night time.
Automatic PIR Light technology helps to save power by 60% during night time.
A normal PIR light costs like around Rs.1000 to 15000. I will explain you the circuits behind it. But use it for your own purpose. Do not SELL.
Test included: 45W mercury bulb. 230V AC
This circuits has two loops. One loop contains the low voltage PIR sensor circuit. The other loop contains 230V circuit.
The low +5V is obtained by a simple circuit including a Bridge rectifier.(D1,D2,D3,D4) Coupled with capacitor filter C1 to bypass any AC ripples in dc output from the bridge rectifier.
LM7805 Regulator IC is a linear based regulator system. Standardized to give +5V output at any input >+5v to +18v at 1A current max support.
The PIR (Passive Infra Red) Sensor also called Motion detector Sensor is our main source of detecting human motion.
To make things simple a PIR sensor acutally calculates difference in infra red radiation in a given space. Human skin radiates some of infra red rays causing a trigger.
This calculations are not important for your knowledge. But there are modules already available for your applications where when detecting human it will directly set a high output for your processing purpose.
This high output is then given to the base of the transistor Q1 (2N2222) power transistor NPN with a current limiting resistor R1 (10k). The relay is connected across the collector.
Relay specifications:
G5LE 5VDC 10A max 250V AC switching rating. DC upto 50V
The diode D5 (1n4148) is a fast switching diode, which is used as a Flyback diode to protect the circuit from back emf from the relay.
The connections on relay are made in such a way that when the motion is detected the relay will click as if you are manually turning a switch ON.
The light will remain on till the motion is detecting. When motion stops, the light will remain on for 10 Seconds and go off. Which can be adjusted on the PIR circuit. PIR sensors are available on www.robokits.co.in and www.onlinetps.com
PROS:
1. You save 60% power on high watt bulbs daily on staircases and other less crowdy lanes
2. Sensor is very accurate to slight motion even in dark so advantage for theft protection systems.
3. Since its relay driven. Changing the type of relay can improve your driving load upto 450v AC max. at 50Amps. You can also make use of TRIAC'S for higher voltages. But I do not recommend that for basic home circuits.
5. Components are widely available and are very common.
6. Cheaper than PIR lights available in market.
CONS:
1. PIR sensor expensive. Rs 400+
2. If you stand still the motion sensor is useless.
3. Transformer consumes 2% of power everytime its ON
4. You have to switch it off in the morning (can be controlled using LDR sensing circuits for day factor)
5. This circuit will turn off the light so total darkness around till you come in sensor range ( can be improved by providing another relay with LED's for atleast some light)
Good luck saving power.
I will improvise my designs in the next post. Thank you for reading.
Macjan Camilo Fernandes
Firmware Development Engineer (R & D)
PIR Motion Dectector based Automatic Staircase Light